EMBARGOED UNTIL JAN. 23 AT NOON E.S.T.Nerve cells in the skin of a mouse ear light up when activated. Application of capsaicin activates only pain-sensing nerve cells, in a dose-dependent fashion, while potassium chloride (KCl) activates all nerve cells present. The video shows more nerves lighting up each time during the sequential application of a low dose of capsaicin, a higher dose of capsaicin (6 sec), and then KCl (10 sec). Credit: Yushim Kim and Xinzhong Dong (courtesy of Neuron)